1. Field of the Invention
The present invention relates to the field of injection devices, and particularly to devices and methods for controlling dosages other than by visually reading a measurement scale.
2. Prior Art
Certain ailments and maladies are susceptible of control by occasional injection of a suitable drug in accordance with either a predetermined dosage and schedule or in accordance with certain physiological measurements. One such disease is diabetes, which may be maintained under reasonable control by reasonably frequent injections of insulin. These injections may be relatively easily administered, and in order to provide maximum mobility of the patient, they are often administered by the patient himself.
Impaired vision often accompanies diabetes, and therefore injection measurements which depend upon the visual reading of a scale or other indicia by the person administering his own injection is likely to result in large errors on occasion. Accordingly, it is this specific problem to which the preferred embodiment of the present invention is directed, though it is to be understood that the present invention may be used whenever non-visual dosage control for syringes is necessary or desired.
There are a number of devices which have been proposed to solve the foregoing problem. Some of these known devices are devices for mating over the cylinder of the syringe, such as that disclosed in U.S. Pat. No. 2,739, 589 and U.S. Pat. No. 2,943,624. Other devices are devices to be used in conjunction with a standard syringe but not fastened thereto, such as are disclosed in U.S. Pat. Nos. 3,610,241 and 3,770,026.
A device for use in dosage control by persons with impaired vision preferably should have certain characteristics generally not found in the prior art devices. It should be small and readily carried by the user. It should be usable with standard syringes, as the cost associated with special syringes or devices forming a part of a special syringe would normally be prohibitive. It should also be readily adjusted by a doctor or other person of normal vision and yet not subject to inadvertent loss of adjustment by slippage, etc., which is not likely to be detected by persons of impaired vision.